Child safety seats (sometimes referred to as safety seat, child restraint system, and restraint car seat) are seats designed specifically to protect children from injury or death during collisions. These seats are typically purchased and mounted by consumers over an existing vehicle seat (e.g., a car seat), and are secured to the vehicle seat by way of the vehicle's seat belt harness. Many regions require children defined by age, weight, and/or height to use a specific government-approved child safety seat, resulting is several classes of child safety seats including rear-facing baby (or infant) car seats for children up to 2 years, and front-facing safety seats (sometimes referred to as “booster seats”) for children to age 9 or 90 lbs. The present invention particularly pertains to front-facing safety seats.
All child safety seats must pass rigorous compliance testing before sale to consumers is authorized, for example, by the National Highway Traffic Safety Administration. One area of compliance testing involves measuring chest acceleration and head excursion during rapid deceleration, which measured by strapping a test dummy into a proposed child safety seat product, and then simulating a frontal crash at a regulated speed (e.g., 35 miles per hour). If the test dummy experiences chest acceleration above a predetermined minimum amount (e.g., 60 G's or more), or experiences head excursion greater than a predetermined distance, then the proposed child safety seat product fails testing and is not authorized for sale to the public.
FIGS. 10(A) and 10(B) are simplified perspective views showing a child safety seat 20 as it is mounted and attached to a standard vehicle (car) seat 80 using a conventional single-fixed belt guide approach.
As indicated in FIG. 10(A), vehicle seat 80 includes a base portion 82, an upright (back) portion 83, and is operably disposed relative to an associated safety belt system 90, which would be used in the absence of safety seat 20 to secure an adult passenger to vehicle seat 80 according to known techniques. Specifically, standard safety belt system 90 includes a belt 91 having a shoulder portion 92 that is typically secured at its upper end to a retractor mechanism (not shown), a lap portion 93 that is secured to a first lower anchor (not shown), and a buckle 94 that is detachably received into a buckle latching mechanism 98, which is anchored by way of a short belt 97 to a second lower anchor point (not shown).
Child safety seat 20 generally includes a seat shell 30 having a seat base portion 32 and a seat upright (back) portion 33 that form a seating area S, and a harness system 40 for securing a child to the seat shell 30 in seating area S. Harness system 40 typically includes two belts 45-1 and 45-2 that are secured upper ends to upright portion 33, and secured at lower ends to seat base portion 32, buckles 46-1 and 46-2 that are slidably connected to belts 45-1 and 45-2, respectively, and a quick-release buckle latching mechanism 48, which is secured to seat base portion 32 by way of a center belt strap 47.
According to the conventional single-fixed belt guide approach, safety belt system 90 is utilized to secure safety seat 20 to vehicle seat 80 by way of a pair of guides (or openings) 34-1 and 34-2 are formed in the seat upright portion 33 of safety seat 20. Specifically, as indicated in FIG. 10(B), a portion of belt 91 including buckle 94 is fed through guide 34-1, passed along a horizontal belt path HBP defined between guide 34-1 and guide 34-2, and fed back out of guide 34-2. With safety seat 20 mounted onto vehicle seat 80 in the manner shown in FIG. 10(B), buckle 94 is then secured into buckle latching mechanism 98, and shoulder belt portion 92 is pulled to take up any remaining slack, thereby securing safety seat 20 to vehicle seat 80. In this secured state, horizontal sections 92H and 93H of shoulder belt portion 92 and lap belt portion 93, respectively, are located in and extend substantially horizontally along horizontal belt path HBP, and are disposed behind seating area S (or in seating area S, but behind a seated child, not shown).
FIGS. 11(A) and 11(B) show safety seat 20 secured to vehicle seat 80 from a cross-sectional side view (i.e., viewing fixed horizontal belt path HBP along the length of horizontal belt sections 92H and 93H), and depict the change in a child's center of gravity (CG) as the child grows. FIG. 11(A) depicts a younger (smaller) child C1 secured in safety seat 20 by way of harness system 40, and FIG. 11(A) depicts an older (taller) child C2 (e.g., child C1 after a period of growth) secured in safety seat 20 by way of harness system 40. As indicated, younger child C1 has a center-of-gravity CG1 that is located at a first distance H1 above seat base portion 32, and older child C2 has a CG location CG2 that is at a second distance H2 above seat base portion 32, where second distance CG2 is greater than distance CG1. That is, as a child grows, the child's CG gradually changes from distance H1 to distance H2 (i.e., the child's CG moves further away from seat base portion 32).
As also indicated in FIGS. 11(A) and 11(B), the conventional single-fixed belt guide approach utilizes a fixed horizontal belt path HBP in which the distance H is typically located at an anticipated midpoint between the lower CG location CG1 of a younger (smaller) child C1 (shown in FIG. 11(A)), and the higher CG location CG2 of an older (taller) child C2 (shown in FIG. 11(B)). That is, fixed horizontal belt path HBP is typically set above lower CG location CG1 of a younger (smaller) child C1 (as shown in FIG. 11(A)), and below the higher CG location CG2 of an older (taller) child C2 (shown in FIG. 11(B)).
A problem with the conventional single-fixed belt guide approach is that utilizing a “midpoint” fixed horizontal belt path can result in injury to both very small and very large children (i.e., children whose center of gravity is below or above the fixed horizontal belt path). That is, the present inventors have determined through extensive experimentation that risk of injury is only minimized when a child's CG is vertically aligned with the fixed horizontal belt path. Specifically, when a child's CG is below the fixed horizontal belt path (as depicted in FIG. 11(A), where CG1 has a height H1 that is below height H of fixed horizontal belt path HBP), the present inventors have determined through experimentation that the younger/smaller child can be subjected to substantially higher chest acceleration during a sudden vehicle deceleration (e.g., during a crash) than would be experienced if the child's CG were vertically aligned with the fixed horizontal belt path. Conversely, when a child's CG is above the fixed horizontal belt path (as depicted in FIG. 11(B)), the present inventors have determined through experimentation that the older/taller child is subjected to greater head excursion during a sudden deceleration, which can result in neck injury, than would be experienced if the child's CG were vertically aligned with the fixed horizontal belt path.
Another problem with the conventional single-fixed belt guide approach is that, because the conventional approach includes only a single-fixed belt guide, there is no way for the conventional approach to minimize risk of injury as a child grows. That is, if a conventional safety seat were provided with a single-fixed belt guide having a relatively low fixed horizontal belt path, then the conventional safety seat may be optimized for a younger/smaller child (i.e., when the child's CG is relatively close to the seat base and aligned with the lower fixed horizontal belt path), but the lower fixed horizontal belt path becomes more and more problematic as the child grows (i.e., as the distance between the child's CG and the seat base gradually increases), thereby subjecting the growing child to gradually increasing head excursion that can result in neck injury. Conversely, if a conventional safety seat were provided with a single-fixed belt guide having a relatively high fixed horizontal belt path, then the conventional safety seat may be optimized for the child when older/larger, but the higher fixed horizontal belt path would be problematic when the child is young (i.e., when the horizontal belt path is higher than the child's CG, as indicate in FIG. 11(A)), thereby subjecting the child to higher chest acceleration during a crash.
What is needed is a child safety seat that avoids the problems associated with the conventional single-fixed belt guide approach. Specifically, what is needed is a child safety seat with a seat belt adjustment mechanism that facilitates vertical adjustment the horizontal belt path with a child's center of gravity, and is economical to produce and easy to use.